The field of the present invention relates to a gas flow type angular velocity sensor which is capable of detecting a deflection of a gas flow in a gas path when an angular velocity acts on the sensor body by sensing a change of resistance in each of paired thermosensitive resistance elements disposed in the gas path.
There has been known such a gas flow type angular velocity sensor for sensing an angular velocity acting on its body, wherein gas is forced by a pump through a nozzle port into a gas path toward a pair of thermosensitive resistance elements (heat wires) arranged at the right and the left in the gas path and a change of differential resistance in the paired heat wires, which is produced when the gas flow is deflected to the left or the right by the action of an angular velocity applied to the sensor body, is detected by an unbalanced output of an angular velocity sensing bridge circuit which includes, in its respective arms, the above-mentioned paired thermosensitive resistance elements and paired reference resistance elements.
This type of angular velocity sensor, however, has a drawback that its detecting accuracy may vary with a change of the flow rate of gas in the gas path because the sensor is designed to determine a deflection of the gas flow by sensing a differential change of resistance in the paired thermosensitive resistances.
Recently, there has also been developed a gas rate sensor of the type which has a body portion composed of a gas path and a pair of heat wires arranged therein and which is manufactured by semiconductor micro-machining on the basis of IC technology. Usually, the sensor uses a small volume of gas in its gas path and its detecting accuracy, therefore, may be greatly affected even by a very small fluctuation of the gas flow.
Accordingly, Japan Laid-Open Patent Publication No. 5-2026 proposes to provide an angular velocity sensor with a flow sensor (additional thermosensitive resistance) in a nozzle portion of the sensor body to detect a flow rate of gas through the nozzle port and to control the operation of a gas injection pump so as to maintain a constant gas flow rate. This solution, however, requires the provision of an additional flow sensor element in the angular velocity sensor body, which complicates the construction of the sensor body.
The sensitivity of the sensor to a change in the gas flow rate may vary with a change in the gas temperature. Therefore, it is also necessary to make a temperature compensation together with the control of the gas flow rate.